Talk of the Nation

In Afghanistan and other conflict zones, the military is often first on the ground, followed by diplomats, contractors and journalists. Next, in many cases, are aid workers: People who work for private organizations and strive to remain impartial in some of the world's most dangerous places.

Reporting in Cell Metabolism, researchers write that when people who lead relatively sedentary lives worked out the DNA in their muscle fibers changed almost immediately. Scientists also found caffeine had the same effect on isolated rodent muscles. Study co-author Juleen Zierath discusses the DNA modifications.

Between the resident emu and the newborn goats, Harvard's Concord Field Station, located in Bedford, Mass., has a menagerie feel. The lab researches how different animals move--which requires lots of animals, and gadgets to facilitate and document their motion.

Reporting in the Astrophysical Journal, scientists write of a massive collision between two galaxy clusters. By studying the cosmic remnants of that smashup, they say leftover dark matter isn't behaving as current theory predicts. Astrophysicist Andisheh Mahdavi discusses this dark matter mystery.

It's been an unusually warm winter in some parts of the country, with springtime temperatures and very little snow. How is nature responding? Purdue entomologist Tom Turpin and horticulturalist Kristin Schleiter of the New York Botanical Garden discuss how an early spring affects flower buds, beetles and bees.